The industry was caught by surprise by the advent of the automatic transmission in the early 1950s. General Motors' Dynaflow, introduced by Buick in 1948, was a smash hit with the public, very soon being fitted in over 80% of new Buicks. (GM's fully-automatic Hydramatic, which debuted in 1939, was in 70% of Pontiacs that year.) Chrysler had previously offered a Fluid Drive torque converter on their manual transmissions, and the Hy-Drive was an evolution of this. It was sold by Plymouth until the fully automatic PowerFlite was available in 1955. About 75,000 cars came equipped with this transmission.